Bally 5000 Plus, Manual

Page: 108 / 388

C i r cu i t Descr i pt i on ( cont ' d )
OUART
The O UART c i r cu i t cons i s t s of a 2
dua I un I ve r s a I async h ronous
r ece i ve r t r ansm i t t e r s ( DUARTs )
They ope r a t e a t 3 . 6864 �Hz and a r e
l oc a t ed a t U 2 3 a n d U 2 2 .
U 2 3 I s s hown and d i scussed w i t h U 2 2
be i ng r ep r esen t e d I n p a r e n t hes i s .
So f t wa r e c h i p se l ec t s U 2 3 and U 2 2 .
See Ch i p Se l ec t I n t h i s Sec t i on .
U 1 0 p i n 1 9 sends t he l oc a l I /O
s i gna l t o U 7 p i n 1 8 .
U7 p i n 2 sends OUARTCS2 t o U 2 3 p i n
35 . ( U7 p i n 1 sends OUARTCS 1 t o U 2 2
p i n 35 )
U 2 3 ( U2 2 ) commun i ca t es t h r ough
t he
b l -d l r e c t l ona l da t a bus
l i nes :
P i n
00 2 5
0 1 1 6
0 2 2 4
03 1 7
04
23
05
1 8
06
2 2
0 7 1 9
So f t wa r e
a d d r esses U23 ( U 2 2 )
t h rough t he a d d r ess
l i nes :
P i n
A1
1
A2
3
A3
5
A4 6
U 1 p i n 9 sends a R /W s i gna l t o U 2 3
( U 2 2 ) p i n 8 .
3 . �PU BOARD
NOT ES
3-5 1